Process for the production of brushware by injection moulding and brushware produced by it

ABSTRACT

The invention is a process for the production of brushware having a plastic bristle carrier and at least one bristle bundle fixed to the carrier and constituted of stretched, stabilized plastic monofilaments. An open injection mould is provided defining a cavity in which the bristle carrier is moulded with one part of the mould having a channel in which at least one bristle bundle is guided with an end of each bristle bundle projecting beyond a mouth of the channel and being melted to a thickening having a cross section greater than a cross section of the channel and the bundle which anchors the bundle to the carrier with the thickening being spaced a distance from the mouth of the channel. The injection mould is closed to define the cavity and a plastic melt is injected into the cavity with the distance of the thickening of the at least one bristle bundle from the mouth of the channel permitting air and any degassing products from the plastic melt to be removed through the channel and being of sufficient length so that a length of thermally weakened monofilaments produced by a molecular reorientation during melting of the end of the at least one bristle bundle to form the thickening area surrounded by the plastic melt without the plastic melt penetrating the channel. The at least one bundle is positioned and fixed in the channel so that the distance, depending upon a diameter of the monofilaments, is between 0.1 mm and 2.O mm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for manufacturing brushwareand brushware.

2. Description of Prior Art

Ever since the first use of plastics both for the bristles and also thebristle carriers of brushware, numerous attempts have been made toreplace the previous mechanical fixing of the bristle bundles to thebristle carrier by a positive or integral connection without any furthermechanical fixing means. These more particularly include injecting in,in which the bundle ends are embedded by injecting round with theplastic melt for the bristle carrier and are fixed to the latter.

An essential quality feature of brushware is the extraction resistanceof the individual bristles or bundles, i.e. the bristles must be soembedded in the plastic mass of the bristle carrier that they are notdetached under the forces occurring during use. Among the knowninjection moulding processes only those have proved usable in whichthere is a thickening on the bundle ends located in the mould and whichafter injecting with the plastic mass of the bristle carrier forms atype of anchor and also interconnects the bristles at their fixing-sideend, so that the extraction forces acting on the bundle or only oncertain individual bristles are introduced into the thickening andabsorbed by the fixing thereof in the bristle carrier.

The known processes use all injection moulds in which one mould half isprovided with a number of channels corresponding to the bristle coverageand through which the bristle bundles can be supplied to such an extentthat the ends of the bundles project into the mould cavity. The bristleends of the bundle are then either interconnected by an adhesive forminga thickening (FR-A-1,453,829/Piotrowski) or, to the extent that they areformed from plastic monofilaments, are melted, the melt solidifying to athickening having a larger cross-section than the bundle (DE845,933/Schiffer).

It is obvious that the extraction resistance of the bristles increasesthe greater the embedding length of the bundle in the bristle carrier.However, this is countered by the following requirements. Both in thecase of bristles, which are generally made from higher-grade plasticssuch as polyamides and for the bristle carrier the amount of materialused must be kept as low as possible, which is to be implemented by acorrespondingly short fixing or clamping of the bristles. Brushware alsoexists where the bristle carrier, for use reasons, must have a minimumwall thickness. This e.g. applies in the case of toothbrushes, so thatdue to the constricted conditions in the mouth a short construction,including the bristle length, is ensured.

In one known process (EP 142,885/Anchor) the bristle fixing length isminimized in that the thickenings obtained by the melting of the bristleends as a result of the injection pressure during the injection of theplastic melt of the bristle carrier are displaced to the opening of thechannel carrying the bundle, so that the fixing length is reduced to thethickness of the thickening and the anchoring of the bundle isexclusively achieved by the plastic mass of the bristle carrierpenetrating into the narrow gap between the thickening and the mouldwall. The further aim of this known process is to seal the channel bymeans of the thickening to prevent the injected plastic melt frompassing out at the edge of the bundle or between the bristles(overspraying) and giving rise to burrs on the finished brush or atleast to an unattractive appearance. This would also influence in anirregular manner the bending behavior of the bristles in the attachmentarea to the bristle carrier. However, this process is unsatisfactory forseveral reasons. Firstly the pressing of the thickening on the bundlechannel is not certain and cannot be guaranteed in a reproduciblemanner. Thus, as a function of the guidance of the injection mouldingmaterial within the mould and as a function of the cross-section of thethickening, particularly its projecting length over the bundle diameter,the thickening can also float within the melt, i.e. partly draws thebundle out of the channel and into the melt, so that neither the sealingeffect, nor a uniform use length outside the bristle carrier can beobtained. The extraction resistance of the bundle is alsounsatisfactory, because the thin material web engaging over thethickening only has a moderate shear strength.

The disadvantages of the process are at least partly removed by anotherknown process (EP 326,634/Coronet), in that, following the formation ofthe thickening, a tensile force is applied to the bundle for sealing thethickening against the channel opening. This leads to the shortestpossible embedding length, which is the same for all the bundles and theso-called overspraying does not occur (penetration of plastic mass intothe channel both between the bundles and also on the outer bundlecircumference). However, the moderate shear strength at the fixing pointof the thickening remains.

In another known process (DE 1,050,304/Beck) overspraying is to beavoided in that all the bristles of the coverage of brushware arecombined into a single package and a plate is shaped onto thefastening-side end and only the border thereof is engaged behind by theplastic mass of the bristle carrier. This construction can proveadvantageous for paintbrushes, artists' brushes, etc., where the actionof a plurality of small bundles is not vital. Thus, this process isrestricted to special brushware. However, here again the cross-sectionavailable for anchoring purposes is very small, so that its shearstrength is unable to satisfy normal stresses and loads.

In the known processes which per se give rise to the best results (EP142,885 and EP 326,634), it has been found that, apart from theaforementioned disadvantages, brushware and in particular toothbrushesproduced according thereto suffer from other, unexpected qualitydeficiencies. Thus, at the latest after a certain period of use there isan expansion of the bundles and a significant deterioration of therecovery of the bristles, i.e. the bending strength of the individualbristles is clearly reduced in these processes, which does not occurwith a greater embedding length. In that case (DE 845,993, FR1,453,829), apart from the disadvantageously high material use, thereare also other disadvantageous effects. For example, occasionallyfollowing mould removal it is found that the bundles are not parallel toone another or at right angles to the fastening-side surface of thebristle carrier and have instead tilted with respect to their desiredposition or there has been a distortion of the bristles in the areawhere they are embedded.

In the case of the greater embedding length, which is preferable for usereasons, it is necessary to prevent overspraying and the resulting burrformation. Thus, in connection with this process sealing measures havebeen proposed in that into the bundles located in the channel is drivena mandrel in order to tightly compress the bristles in the channel (DE3,832,520/Schiffer). In another known process (DE 2,922,877/Zahoransky)the channel tapers towards the mould cavity and the bundles are pressedinto the constriction. In addition, compressed air acts on the channelfrom the outside.

In all the known processes operating with additional sealing measures,even if they lead to a per se desired, greater fixing length, qualitydeficiencies are still encountered on the product. On the surface of thebristle carrier in the bristle bundle attachment area overspraying andunevennesses occur, particularly in the form of material peaks, cracksand cavities and the burrs and edges resulting therefrom. In sectionoccasionally shrink-holes appear. These surface defects are particularlyundesired in the case of toothbrushes due to possible damage to themucous membranes, but also in the case of body brushes. Toothbrushes orbody brushes suffering from these deficiencies do not satisfy hygienicrequirements, because undesired deposits occur and in particular thereis nidification and a propagation of bacteria. Finally, once again theextraction resistance is reduced.

SUMMARY OF THE INVENTION

The invention is a process for production of brushware in which aminimum amount of material is used while providing an adequateextraction resistance of bristle bundles of the brushware and alsoadequate individual bristles are obtained, in which the bendingelasticity and recovery of the bristles are maintained and asatisfactory surface is achieved in the attachment area on the bristlecarrier. Brushware satisfying these requirements is also to be provided.

The invention is based on the per se known finding that the bendingstrength or bending. elasticity (recovery) of the bristles obtained bystretching and thermally stabilizing the monofilaments is impaired bythe melting of the bristle ends in connection with the formation of thethickening. In the immediate attachment area of the bristles to thethickening there is a molecular reorientation and consequently in thisarea a deterioration of the bending behavior of the individual bristles,as well as to a decrease in the tensile strength occurs. Thedeterioration of the bending behavior in the case of the known processeswith sealing of the thickening on the channel leads to the expansion ofthe bundles. As a result of the process according to the invention, withthe minimum possible material use for the bristles and bristle carrierthe thermally weakened area of the bristles is embedded, so that overtheir free length outside the bristle carrier the bristles fullymaintain the characteristics resulting from the stretching and thermalstabilization. The extraction resistance of the individual bristles isalso improved, because the weakened area is fixed.

The length which is thermally damaged during the melting of the bundleis dependent on several factors, particularly the melting point and theduration of the heating action, the nature of the plastic and themonofilament diameter. It is easily possible to establish the damagedlength on a single bundle in a preliminary test by melting the bundleend and also a few alternating bending loads or stresses, so that thenecessary embedding length for the injection moulding process for theproduct to be produced can be established.

The knowledge of the thermal damage to the bristles, even if in adifferent context, namely the welding of bristles and bristle carriers,is known (DE 9,206,990 U1/Bickel). Account is taken thereof by acomplicated construction of the brush, in that the brush body isprovided with a depression on the bristle side. The bristles are weldedonto a thin plastic plate, which is placed in the depression and coveredby a perforated plate threaded over the bundles. The bundles aresupposed to be laterally supported in the holes of the plate. Finallyseparate parts are required for bracing the perforated plate and thebundle plate with the brush body. Such a brush cannot be manufactured atan acceptable cost level and due to the edges and gaps fails to satisfythe physiological and hygienic requirements made in connection withtoothbrushes or body brushes. It can also not solve the problem of theextraction strength of the individual bristles.

In the process according to the invention the thermally damaged area isembedded exclusively by surrounding with the plastic of the bristlecarrier. The embedding length of the bundles is determined by thedistance between the thickening and the mouth of the channel. However,according to the invention this distance must satisfy a furthercondition. Thus, it must at least be sufficiently large for the airdisplaced during the injection moulding process in the mould cavity andwhich preferably migrates into depressions, cracks, etc. and thereforealso behind the thickening on the bristle bundle, to be able to escapethrough the channel and optionally also between the bristles, because itis probably responsible for the cavities, shrink-holes, etc. on thebundle attachment point observed in the known processes. The sameapplies regarding any degassing products of the melt("Kunststoff-Lexikon", 6th edition, Carl Hanser Verlag). Thus, theprocess of the invention also removes these disadvantages. However, thedistance between the thickening and the channel mouth must not be solarge that overspraying occurs. The invention fixes the essentialparameters for the dimensioning of the smallest possible distance,namely embedding the thermally weakened length area of the bristlesensuring a completely satisfactory venting of the mould in the vicinityof the embedding in order to avoid cavities, shrink-holes, etc. andobtaining a smooth surface on the bristle carrier to avoid overspraying.The invention has in particular recognized that the sealing of thebundle channels which has been required of late in injection technologyis not necessary.

Practical tests have revealed that in the case of standard brushware,the parameters prescribed by the invention are obtained if the bundle isso positioned and fixed in the channel that the distance between thethickening and the channel mouth is 2 to 5 times the bristle diameter.This can be numerically defined in such a way that the distance in thecase of bristle diameters up to 0.3 mm is between 0.1 and 1.0 mm,preferably up to 0.4 mm and in the case of larger diameters between 0.5to 2.0 mm is preferably set up to 1.5 mm.

In order to on the one hand ensure the venting of the mould and on theother to avoid overspraying, according to an embodiment use is made ofbundles, in which the sum of the cross-sections of the bristles of abundle is between 50 and 75% of the cross-section of the channelcarrying the bundle.

In this construction the capillaries between the bristles on the onehand and between the latter and the channel wall on the other aresufficiently large to permit a completely satisfactory venting of themould, particularly in the vicinity of the undercuts present on thethickenings, but is also narrow enough to prevent the plastic melt,which must be solidified as rapidly as possible in the vicinity of thebundle attachment by suitable technological measures (guiding andcontrolling the and controlling the cooling of the mould, materialselection in the vicinity of the bundle channels, guiding the injectionspeed and pressure, etc.) from penetrating the bristle capillaries orthe channel.

The parameters to be respected according to the invention can be fixedby another practicable quantity, in that the bundle in the channel is sopositioned and fixed that the distance between the thickening and thechannel mouth is 20 to 50% of the channel diameter and the channelfilling level given in the previously mentioned embodiment must also beimplemented.

In the practical performance of the process the procedure is preferablysuch that the bundle is introduced into the channel to such an extentthat its end has a distance "A" from the channel mouth, is then meltedby a length "L"<"A", so that the thickening has a distance "B" from thechannel mouth and that the bundle is subsequently drawn back into thechannel until the thickening reaches the desired distance "C"<"B" fromthe channel mouth.

Using this procedure the desired, smallest possible distance can be setin a particularly simple and accurate manner. It is fundamentallypossible to provide the channels carrying or guiding the bundlesdirectly in one mould half of the injection mould and to form thethickening on the bundle end with the mould opened. However, it ispreferable for the bundle to be melted and positioned to the thickeningin a holder having the channel and located outside the mould at the endthereof and subsequently the holder with the positioned bundle issealingly connected to the injection mould, whilst supplementing the onemould half. This procedure has the advantage that the preparatory workon the bundle does not take place on the injection mould which becomesheated in permanent operation, but instead outside the same. This avoidsdamage to the bristles by the heat emission of the injection mould andensures a rapid solidification of the plastic melt at the bundle end andin the vicinity of the holder, thereby preventing overspraying.

This process can be optimized in that the holder on its transportingpath from and to the injection mould and optionally the bundle followingthe formation of the thickening are cooled, so that the bundle andholder are always kept at a constant, low and controllable temperatureand can be supplied in this state to the injection mould.

The problem solved by the invention in the aforementioned process canalso be solved in that following the melting of the bundle end theformed still soft-plastic mass is shaped in the direction of thebristles in such a way that displacement thereof occurs between the massand along the bundle circumference and surrounds the bristles over atleast part of their length area thermally weakened by molecularreorientation during the melting of the monofilaments.

In this process at least one part of the weakened length area of thebristles is directly embedded and stabilized by the bristle material byshaping the still soft plastic thickening. As a result the overallbedding length of bundle and thickening can be further reduced.

This process can also be modified in such a way that the bundle isintroduced into the channel to such an extent that after the formationand shaping of the thickening, the latter has such a distance from thechannel mouth, that the length area of the monofilaments weakened bymolecular reorientation during monofilament melting is partly surroundedby the mass displaced from the melted monofilaments during the shapingof the thickening and in part by the injected plastic melt of thebristle carrier, without the plastic melt penetrating the channel.

The partial length of the bristles not surrounded by the displacedmaterial of the thickening need only be dimensioned in such a way inthis process that the desired venting through the channel takes place inthe vicinity of the bundle and overspraying is avoided.

The completely satisfactory venting of the mould cavity, particularly inthe vicinity of the bundle attachments, as well as the prevention ofoverspraying are, in a further embodiment, assisted in that theinjection speed decreases from a maximum value at the start of injectionto the complete filling of the injection mould and that the normallyapplied subsequent pressure is raised from an initially low value to ahigher value.

The measure provided in another variant acts in the same way in that themould half having the channel has in the vicinity of the channel mouth acontour concentric thereto and which in the area between the thickeningand the channel mouth through a lengthening of the plastic melt flowpath brings about a reduction of its flow rate and speeds up the coolingof the plastic melt in this area.

A lengthening of the flow path in the vicinity of the bundle can beconstructively brought about in that the contour is formed by a collarlengthening the channel into the mould cavity, or in that the contour isformed by a depression in the mould wall and the channel mouth islocated on the bottom of the depression.

By means of the procedure according to the invention not only is itpossible to produce top quality products, particularly toothbrushes,with minimum wastage, but also it is possible to use injection moulding,which leads to top quality brushes with respect to the general surfacecharacteristics of the handle. Thus, e.g. a toothbrush can be moulded inthe vicinity of the handle end, which normally requires a high injectionpressure in order to completely fill the mould cavity. This highinjection pressure in turn leads to a corresponding pressure build-up inthe air contained in the cavity, which is completely satisfactorilyremoved by the setting of the distance between the thickening and theedge of the channel mouth according to the invention. In particular itis possible to avoid other venting measures, either via the separatingsurface of the injection mould, or additional venting ducts, i.e. themould can be so tightly sealed that no burrs form in the separatingsurface and there are also no additional moulding points on the bristlecarrier surface.

In the case of brushware, the set problem is solved in that thethickening has a distance from the bundleside bristle carrier surfacewhich roughly corresponds to the length area of the bristles thermallyweakened during the melting of the monofilaments.

BRIEF DESCRIPTION OF THE DRAWING

The invention is described in greater detail hereinafter relative toembodiments of the process of the invention by means of the attacheddrawings, wherein show:

FIGS. 1-3 show the production of the thickening with an indication ofthe apparatus required in FIGS. 1a, 2a and 3a and a larger-scale view ofthe working area in FIGS. 1b, 2b and 3b.

FIG. 4 is a diagrammatic view of an injection mould during injection.

FIG. 5 is a diagrammatic view during the mould removal of the brush.

FIGS. 6 and 7 show another variant of the process for producing thethickening with the necessary apparatus parts in FIGS. 6a and 7a and alarger-scale view of the working area in FIGS. 6b and 7b.

FIGS. 8 to 10 show other variants of the process in a diagrammaticrepresentation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1a to 3a show two spaced perforated plates 1 and 2 of a bundlecassette between which is located a clamping plate 4 displaceable inaccordance with the direction arrow 3. The perforation pattern of theperforated plates 1 and 2 and the clamping plate 4 corresponds to thebundle arrangement of the bristle coverage to be produced.

With the clamping plate 4 open, the bristles 5 in the form of a bundleand namely as short cuts or taken from the endless strand, areintroduced into the holes of the guide plate 1,2 and the clamping plate4 until the end of the bristle project past plate 4 by a certain amount.A heating device 6 FIG. 2A is then moved in front of the projectingbundle end and heats the bristle ends in contactless manner and meltsthe same, so that a thickening forms (FIG. 2a). The clamping plate 4 isthen moved into the open position (FIG. 3a) and the bundle is positionedby a slider 8 acting on the thickening 7 and then the clamping plate ismoved into the closed position (not illustrated).

In the larger-scale view of FIG. 1b it can be seen that during thesupply of the bundle the bristles 5 project past the perforated plate 2by the amount "A". On melting, the bristle ends according to FIG. 2a aremelted over the length "L" (FIG. 1b), so that the thickening 7 whichforms has a minimum distance "B" from the perforated plate 2. By meansof the slider 8 (FIG. 3a) the thickening 7 is then moved in thedirection of the perforated plate 2 until it has the desired distance"C" from the surface thereof (FIG. 3b).

The thus fixed bundle is then linked to one mould half 10 of aninjection mould 11 by means of the cassette formed by the perforatedplates 1,2 and the clamping plate 4 and using a centering/alignment tool9, the cassette terminating the moulding nest of the mould half 10.After closing the mould through the second mould half 12 by means of theextrusion or injection head 13 the plastic melt is injected for thebristle carrier and it flows around the bundle ends projecting into themould cavity, i.e. the thickening 7 and the bristles over the length "C"(FIG. 3b). The displaced air escapes through the holes of the perforatedplate 2 forming the bundle channel and the bristles 5 are surroundedover the length "C" by the plastic melt, without the latter penetratingthe bundle channel of the perforated plate 2. When the bristle carrieror the brush handle has adequately cooled, the cassette comprising theperforated plates 1,2 and the clamping plate 4 is moved away, the mouldhalf 10 is raised and the finished brush 14 is ejected.

In the embodiment according to FIG. 6a the perforated plate 2 has aconcentric collar 15 projecting into the mould frame. The bristles 5 areintroduced into the perforated plates 1,2 and clamping plate 4 in theopen position thereof, in the same way as described relative to FIG. 1a.The bristle ends projecting over the perforated plate 2 are melted bymeans of a combined heating and shaping device 16 and the melt is shapedat the collar 15, so that once again a thickening 7 is formed, whosediameter "D" after melting is initially slightly larger than the bundlediameter (FIG. 6b) and is increased to the diameter "E" by shaping.After shaping the bristles 3 or the bundle formed by them are moved inthe direction of the mould cavity by means of the slider 17, with theclamping plate 3 open, until the thickening 7 has the distance "C" (cf.FIG. 3b) from the collar 15 of the perforated plate 2 (FIG. 7b). Theshaping of the still soft plastic melt of the thickening 7 can also takeplace in such a way that the soft plastic material between the bristlesweakened by the heat treatment and on the outer circumference of thebundle is displaced in the direction of the bristles, as shown in FIGS.8 to 10. As a result at least part of the thermally weakened length ofthe bristles 5 is embedded by the bristle material, as can be seen inareas 18 in FIG. 10.

In order to prevent overspraying and bring about in the vicinity of thebundle attachment a faster cooling of the bristle carrier plastic melt,the mould half or the perforated plate 2 has in the vicinity of thebundle channel a flow path-lengthening, concentric contour, e.g. thecollar 15 (FIG. 8) or a corresponding depression 19, at whose bottomthen issues the bundle channel.

The invention claimed is:
 1. A process for the production of brushwarehaving a plastic bristle carrier and at least one bristle bundle fixedto the carrier and constituted of stretched, stabilized plasticmonofilaments comprising:providing an open injection mould defining acavity in which the bristle carrier is moulded with one part of themould having a channel in which at least one bristle bundle is guidedwith an end of each bristle bundle projecting beyond a mouth of thechannel and being melted to a thickening having a cross section greaterthan a cross section of the channel and the bundle which anchors thebundle to the carrier with the thickening being spaced a distance fromthe mouth of the channel; and closing the injection mould to define thecavity and injecting a plastic melt into the cavity with the distance ofthe thickening of the at least one bristle bundle from the mouth of thechannel permitting air and any degassing products from the plastic meltto be removed through the channel and being of sufficient length so thata length of thermally weakened monofilaments produced by a molecularreorientation during melting of the end of the at least one bristlebundle to form the thickening are surrounded by the plastic melt withoutthe plastic melt penetrating the channel and wherein the at least onebundle is positioned and fixed in the channel so that the distance,depending upon a diameter of the monofilaments, is between 0.1 mm and2.0 mm.
 2. A process according to claim 1, wherein the at least onebundle is so positioned and fixed in the channel so that the distancefrom the thickening to the mouth of the channel is 2 to 5 times adiameter of the bristles.
 3. A process according to claim 1, wherein thedistance from the thickening to the mouth of the channel for bristleshaving diameters up to 0.3 mm is between 0.1 mm and 1.0 mm, and forbristles having diameters larger than 0.3 mm the distance from thethickening to the mouth of the channel is from 0.5 mm to 2.0 mm.
 4. Aprocess in accordance with claim 3, wherein for diameters of up to 0.3mm the distance from the thickening to the mouth of the channel is from0.1 mm to 0.4 mm and for diameters larger than 0.3 mm the distance fromthe thickening to the mouth of the channel is from 0.5 mm to 1.5 mm. 5.A process according to claim 1, wherein the at least one bundle ispositioned and fixed in the channel so that the distance from thethickening to the mouth of the channel is in a range from 20% to 50% ofa diameter of the channel.
 6. A process according to claim 1, wherein asum of a, cross-section of the bristles of one bundle of the at leastone bundle is from 60% to 75% of a cross-section of the channel.
 7. Aprocess according to claim 1, wherein the at least one bundle isinserted into the channel so that the end thereof has a distance A fromthe mouth of the channel, is then melted to a length L with L<A, so thatthe thickening has a distance B from the mouth of the channel and thebundle is then drawn back into the channel until the thickening has thedistance C from the mouth of the channel with C<B.
 8. A processaccording to claim 1, wherein the bundle is melted at the end thereof toform the thickening and is positioned outside the injection mould in aholder containing the channel and then the holder holding the positionedbundle in association with one part of the mould is sealingly connectedto the injection mould.
 9. A process according to claim 8, wherein theholder and the bundle have a transporting path and the bundle held inthe holder following formation of the thickening during motion along thetransporting path undergoes cooling.
 10. A process according to claim 1,wherein after melting the end of the at least one bundle, the softplastic material of the at least one bundle is shaped in the directionof the bristles and is displaced between the bristles and along a bundlecircumference and surrounds the bristles over at least part of a lengththereof which is thermally weakened by molecular reorientation duringmelting of the monofilaments.
 11. A process according to claim 10,wherein the bundle is introduced into the channel to such an extent thatfollowing formation and shaping of the thickening the bundle is spaced adistance from the mouth of the channel that a length of themonofilaments weakened by the molecular reorientation during melting ofthe ends of monofilaments is partly surrounded by material displacedfrom the melted monofilaments during shaping of the thickening andpartly by the injected plastic melt of the bristle carrier without theplastic melt penetrating the channel.
 12. A process according to claim1, wherein a speed of injection is reduced from a maximum value at astart of injection to a time of complete filling of the injection mouldand a pressure applied subsequently to the complete filling of the mouldis raised from an initially lower value to a higher value.
 13. A processaccording to claim 1, wherein a mould part having the channel in avicinity of the mouth thereof has a concentric contour and in a locationbetween the thickening and the channel mouth a lengthening of the flowpath of the plastic melt reduces a flow rate and a cooling of theplastic melt is speeded up in the location between the thickening andthe channel mouth.
 14. A process according to claim 13, wherein thecontour is formed by a collar extending the channel into the cavity ofthe mould.
 15. A process according to claim 13, wherein the contour isformed by a depression in a wall of the mould and the mouth of thechannel is located on a bottom of the depression.